1. Field of the Invention
The present invention relates to package structures, and, more particularly, to a package structure having MEMS (micro-electro-mechanical system) elements and a fabrication method thereof.
2. Description of Related Art
MEMS elements have integrated electrical and mechanical functions and can be fabricated via various micro-fabrication technologies. A MEMS element can be disposed on a substrate and covered by a shield or packaged with an underfill adhesive so as to form a MEMS package structure.
FIG. 1 shows a cross-sectional view of a conventional package structure having a MEMS element. Referring to FIG. 1A, a MEMS element 11, such as a pressure sensing element, is disposed on an LGA (land grid array) substrate 10 and conductive pads 111 of the MEMS element 11 are electrically connected to conductive pads 101 of the LGA substrate 10 via a plurality of bonding wires. Further, a metal lid 12 is disposed on the substrate 10 for covering the MEMS element 11 so as to protect the MEMS element 11 against external damage and pollution. However, such a package structure has a large size and cannot meet the demand for lighter, thinner and smaller electronic products.
Accordingly, FIG. 2 shows a wafer-level package structure as disclosed by US Patent Application No. 2006/0185429. Referring to FIG. 2, MEMS elements 11 such as pressure sensing elements are directly formed on a silicon substrate 13, and glass lids 14 are bonded to the MEMS elements 11 via anodic bonding.
Further, the silicon substrate 13 has sensing cavities 131 and through holes 132 formed therein by using TSV (through silicon via) technology. Such a TSV technology uses KOH as an etchant for forming the through holes or recesses.
Compared with the previously described package structure, the present package structure has a greatly reduced size. However, the TSV technology for forming the through holes and recesses is costly and requires a high degree of accuracy, thus complicating the fabrication process and increasing the fabrication cost.
Therefore, it is imperative to provide a package structure having MEMS elements so as to overcome the above-described drawbacks.